Cannula



FIG. 1 is a perspective view of a cannula incorporating the design;

FIG. 2 is a side elevational view of the design of FIG. 1, the left side and the right side elevation having the same appearance;

FIG. 3 is a top plan view of the design of FIG. 1; and,

FIG. 4 is a bottom plan view of the design of FIG. 1. 

The ornamental design for a cannula, as shown and described. 